This invention relates to novel actuator carriage means.
Magnetic disk files for recording and storing data are widely used in data processing; e.g., as peripheral memory. Disk files have the advantage of facilitating data transfer at randomly selected address locations (tracks), yet rapidly.
The transducers used in association with disk recording surfaces must be reciprocated very rapidly between selected address locations (tracks) with high precision. It will be recognized as important for such a system to move a transducer very rapidly between data locations; and to do so with high positional accuracy between closely-spaced track addresses. This constraint becomes very tricky as track density increases. Typically, such disk storage systems mount the transducer head on an arm carried by a block that is supported by a carriage. This carriage is usually mounted on track ways for reciprocation by an associated transducer actuator. This disclosure relates to improving such carriages.
The present trend is toward ever higher track density with increased storage capacity and decreased access time. Of course, as track density rises, closer control over the actuator mechanism is necessary to position transducer heads accurately over any selected track; also the carriage and other actuator parts must be made yet simpler and lighter to accommodate such fast accurate positioning. This disclosure concerns improved means of mounting a carriage on its track ways.
Known positioners:
Such transducer actuators (linear positioners) employed with magnetic disk memory systems are subject to stringent requirements; for instance, these systems typically involve a stack of several magnetic disks, each with many hundreds of concentric recording tracks spanning a radius of 4-12 inches; and a head-carrying arm is typically provided to access each pair of opposing disk surfaces. This arm will typically carry two to four heads so that it need be moved only about 2-3 inches (radially) to position its head adjacent any selected track. Thus, it will be appreciated that such applications involve extreme positioning accuracy together with very high translation speeds (to minimize access time--a significant portion of which is used for head positioning). Such a positioner must move its transducer heads very rapidly so that the associated computer can process data as fast as possible--computer time being so expensive that any significant delay over an extended period (of even a fraction of a millisecond) can raise costs enormously ("transition time", during which heads are moved from track to track, is "dead time" insofar as data processing is concerned, of course).
Thus, computer manufacturers typically set specifications that require such inter-track movements to take no more than a few milliseconds. Such high speed translation imposes extreme design requirements; it postulates a powerful motor of relatively low mass (including carriage weight) and low translational friction.
Another requirement for such head positioners is that they exhibit a relatively long stroke, on the order of 0.5-4 inches or more, in order to minimize the number of heads required per recording surface.
The prior art discloses many such positioner devices, including some intended for use in magnetic disk memory systems: e.g., see U.S. Pat. Nos. 3,135,880; 3,314,057; 3,619,673; 3,922,720; 4,001,889; 4,150,407; 3,544,980; 3,646,536; 3,665,433; 3,666,977; 3,827,081; 4,331,990; 4,414,594 and 3,922,718 among others.
Known actuator approach (FIGS. 7A, 7B):
FIGS. 7A, 7B schematically illustrate a known sort of "flat coil" linear positioner A-m which can be considered as comprised of two primary assemblies: a mobile armature-carriage assembly A-c essentially including flat coils, head mount, roller bearing and support means; plus a fixed housing and permanent magnet structure A-g with the magnet shunts, sides, etc.
As shown in the drawings for purposes of illustration, the invention is to be understood as incorporated in a magnetic disk memory system, including a plurality of disks D in a conventional stacked array Pk, arranged in vertical spaced relation with a related stacked array of head assemblies h. Each head assembly h is mounted at the distal end of an armature carriage A-c to be reciprocated back and forth in its disk-gap relative to a respective pair of magnetic recording disk surfaces.
With selective positioning of each head assembly in a conventional manner, the "flat armature" (coil) means provided may be electrically energized to move into a retracted or extended position as known in the art (relative to associated pair of disk surfaces) and read or record information on any selected track thereof. Thus, the head assemblies h are supported in pairs on actuator strip A-m, to be projected in cantilever fashion as part of a rolling carriage supported by rollers r and movable along track rails R. The reciprocating actuator assembly A-m, carrying coil C, is operable when coil C is current-energized in a conventional manner, to move the carriage along the associated cavity, toward and away from the disk stack between a plurality of precisely located addresses, these addresses, or track positions, determine the position of heads within the stack in the known manner. The opposite (rear) end of the actuators includes their flexible connector (head cable) means, and associated connections, these being provided conventionally and as known in the art.
As detailed in FIG. 7, each actuator strip A-m includes two double roller assemblies r on each side thereof (or two such opposed by a single third roller as an option). These dual-opposed wheels are adapted, as known in the art, to engage a respective guide rail R as indicated in FIG. 7B in rolling contact when the assembly A-m is translated along its elongate axis (in moving head assembly h relative to track addresses on a respective pair of disks D as well known in the art). Each actuator strip A-m is adapted to be so-reciprocated along a respective actuator cavity between opposed sets of permanent magnet poles m.
FIG. 7 also illustrates details of such a flat coil actuator strip A-c where, according to various further features, the strip is formed into a relatively thin, light-weight, planar body and is adapted to receive flat coil winds (preferably as a printed circuit board PCB, with two or more flat, overlapped coils C printed thereon). Electronic circuit means e is also preferably mounted on each strip A-c at the designer's option (e.g., read/write electronics for the associated actuator).
Such a "flat armature" A-m will be understood to comprise a "planar trolley" carrying read/write heads h at its distal end and mounted on bearings to be reciprocated freely along a track between upper and lower relatively flat opposing pole pairs.
The instant teaching illustrates ways to improve such actuator carriages (e.g., FIGS. 7A, 7B), especially in making (some) roller means thereof "flexible" and better able to engage related rail means.
In accordance with one salient aspect of the present invention, such a transducer positioner is formed to comprise a thin flat "planar" carriage. In one embodiment, the carriage is comprised o a thin, planar frame carrying wire loops as driving coils.
It will be readily apparent to workers how such a "planar carriage" can provide the moving coil structure for an improved linear actuator, compressing it and flattening it out, as well as facilitating a great reduction in mass and volume. Such an improved armature will be seen to give superior performance.
According to a feature hereof such planar carriages are provided, one for each disk gap, in integral relation with a direct-access disk drive apparatus. In such an apparatus the linear positioning operates responsive to electrical signals to its coils causing it to carry heads between disk track addresses. Such a "planar carriage" positioner will be understood and described below as comprising a movable, planar non-magnetic frame on which coils are disposed, this frame being adapted to be reciprocated along the "magnet gap" between an array of stationary permanent magnet means responsive to certain current through the coil windings.
Thus, an electrical address signal to the coils may be directly converted into linear actuator motion providing high speed head translation. Such an "armature" will be seen to eliminate much unnecessary mass and reduce associated power and actuator volume (e.g., the wound coil may be potted and form an extension of the carriage frame for carrying a set of recording heads and eliminates all intermediate means and their associated mass and complications.
In a related feature, it will be seen that such planar carriage means include roll bearings (as wheels riding on associated track-ways) which are improved to be better engaged with their guide means (track-ways) to afford positive track-engagement and retention, full-line contact (alignment), etc. This disclosure is intended to teach such implementation.
Workers are aware that mounting such actuator "trucks" (carriages) for rapid, low-friction precise reciprocation is a particular challenge--especially where reliability and precise positioning must be maintained over millions of high-acceleration cycles, yet while minimizing cost of fabrication. And, with such a truck mounted on a roller (or like wheel means) to recrprocate along track means, it is a particular challenge to get the roller precisely engaged on the track means (cf. "full-line-contact"), and hold it there, despite violent acceleration.
Of course, one could make or buy "perfectly aligned" roll means and track means, and could individually match them to one another--but this is quite expensive and not well-suited to mass-fabrication or the use of off-the-shelf components. Also, one would still want to bias the roll means against the rail means (or vice versa).
Such problems are alleviated, according to this teaching, by making some roll means flexible--particularly where roller means are so mounted on their rotation-shaft as to "bend" or be compliantly shifted by bias-engagement with their rail means so as to assume better, full-line contact therewith.
Thus, one object of this invention is to provide the mentioned and other features and advantages. Another object is to teach the use of such "planar carriage actuators" in transducer assemblies, especially as adapted for positioning heads in a disk drive. A related object is to adapt the actuator carriage means to better engage associated guideways.
A further object is to provide multi-arm disk drive positioners which are "modular", one for each disk gap.
Another object is to "miniaturize" head actuators for disk drives; a related object is to reduce their cost, weight and power consumption, while improving acceleration.